The present invention relates to a multi-series connection type battery cell pack that comprises a plurality of series-connected battery cells, a charge/discharge control switch connected between said plurality of battery cells and an output terminal for performing charge/discharge control, a plurality of protective circuits for detecting at least the voltage of each battery cell, and a control circuit for communication with a computing circuit for performing computation of pack detection signals including each detection signal from said plurality of protective circuits and external equipments, thereby performing management and control of signals in the pack including said detection signals. The present invention is also directed to a charger making use of a battery cell pack function to charge a battery cell pack comprising therein a detection circuit for detecting at least the voltages and charging currents of said plurality of battery cells and a control circuit that has a function of communicating with external equipment and converting said detection signals to digital data for management and control purposes.
So far, portable electronic equipments such as cellular phones, notebook personal computers, players and digital cameras have been operated using as power sources a battery cell pack comprising therein a plurality of series-connected rechargeable battery cells, e.g., lithium ion battery cells. For these equipments that do not need any extremely high source voltages, a series connected type battery cell pack comprising four battery cells at most suffices. However, when such a type battery cell pack is intended for use as a power source for electrically aided bicycles that are now enjoying a growing popularity, for instance, a multi-series connection type battery cell pack comprising at least 7 battery cells is needed because the voltage of the four-battery cell pack is unacceptably low.
FIG. 1 is a diagram showing a prior art battery cell pack and how to perform charge control with a charger. Reference numeral 10 is a battery cell pack, 11 cells, 12 a charge/discharge control switch, 13 a protective circuit, 20 a charger, 21 a charging unit, 22 a charge detection unit, 23 a charging power source, and Ri and R1 current detection resistances.
The conventional battery cell pack, and how to perform charge control with a charger is now summarily explained. In addition to the cells 11, the battery cell pack 10 has usually therein the charge/discharge control switch 12 that is series-connected between input/output terminals, the current detection resistance Ri for detection of discharging currents, and the protective circuit 13 for detecting cell voltages and discharging currents, thereby protecting the battery cells against overcharging and over-discharging, as shown in FIG. 1. The charger 20 for charging the cells 11 connected to the battery cell pack 10 is provided with the current detection resistance R1 for detection of charging currents for the battery cell pack 10, the charge detection unit 22 for detection of the charging voltage and current of the battery cell pack 10, and the charging unit 21 for performing control of the charging voltage and current fed from the charging power source 23 to the battery cell pack 10 and control of when to stop charging on the basis of the charging voltage and current detected by the charging detection unit 22.
As explained above, in the battery cell pack 10 there are provided the charge/discharge control switch 12 series-connected between the cells 11 and the input/output terminals and comprising a charge control FET and a discharge control FET, and the protective circuit 13 for controlling a control microcomputer for communicating with outside to manage and control the battery cell pack and detecting the voltages and currents of the cells to control the charge control FET and discharge control FET. For this protective circuit, however, only low-voltage or medium-voltage protective ICs compatible with battery cell packs comprising four cells at most are commercialized because the standard type set for conventional battery cell packs like the battery cell pack 10 is still made up of up to 4 series-connected cells.
In new applications where battery cell packs whose voltage is higher than ever before are needed, as is the case with power sources for the aforesaid electrically aided bicycles, the low- or medium-voltage protective ICs must be connected together in a “protective ICS” unit. On the other hand, a problem with the control microcomputer is that when signals from the respective low- or medium-voltage protective ICs are processed, some inconveniences are caused during computations or communications unless the processing levels are appropriate to the varying voltage references of the low- or medium-voltage protective ICs.
In such applications where a plurality of low- or medium-voltage protective ICs are used, internal power consumptions increase. This in turn leads to another problem that pack storability becomes drastically worse or some packs are susceptible to over-discharging while they are let stand.
For a charger for charging a battery cell pack, on the other hand, a close understanding of the charging voltage and current of the battery cell pack is an important factor in consideration of charging accuracy as well as evaluation of to what degree the battery cell pack deteriorates. For a conventional charger, a high-precision A/D converter or the like must thus be used on a charging unit to detect charging currents, resulting in a complicated, large, expensive circuit. Especially in the case of such a multi-series connection type as set forth above, it is important to have an understanding of the degree of deterioration of each cell in the battery cell pack; in the conventional charger, however, it is impossible to keep track of the degree of deterioration of each cell.